Hamas’ brutal attacks in Israel on October 7 killed at least 1,400 people and the group took more than 200 hostages, according to Israeli authorities. In the wake of the assault, Israel launched an aerial bombardment of Gaza that Palestinian health officials say has killed more than 5,000 people. Israel also announced a “complete siege” on the enclave, withholding vital supplies of water, food and fuel.
I quickly googled some numbers, so no guarantee for 100% correctness.
Desalination uses about 3.6kWh/m3 of water. A generator can produce around 1.5kWh/litre of fuel. 500,000 litres of fuel would result in 750,000 kWh. 750,000 kWh would result in 208,333 m3 or 208,333,000 litres of water. That theoretically would allow you to create around 200 litres per person if you use the entire amount of fuel on water desalination.
But this calculation only works in a hypothetical scenario and not in a real life scenario. Distribution of the water to all the people will require a lot of energy as well, e.g. for tank trucks. And I think in an active war zone you probably won’t find world class logistics.
Furthermore, you also need fuel and electricity for other critical infrastructure: firetrucks, hospitals, phones, cooking, …